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The research facility on the site of the Paul Scherrer Institute looks like a giant UFO. The views inside the building are every bit as unique as the exterior of the building is exotic. With first rate X-ray systems at their disposal, researchers from all around the world examine micro structures and develop new materials or medications.

Oliver Bunk at the SLS: The experimentation hall has a diameter of over 130 metres. Concrete plates shield the particle accelerator. Many billions of electrons rotate a million times a second. When they are braked by magnets, they radiate synchrotron light. (Photo: Kellenberger Kaminski Photographie)

Radar waves have a very long wavelength. One of the physicists, Oliver Bunk, explained that "this enables them to track the arrival of a ship or aircraft. You need X-ray light with a very short wavelength to see crystals, molecules or atoms." The Swiss Light Source, or SLS for short, produces precisely this at the Paul Scherrer Institute (PSI) in the town of Villigen in Aargau. Oliver Bunk is the Director of the Laboratory for Macromolecules and Bioimaging and, among other things, ensures that the researchers at the SLS have outstanding conditions at their disposal for their work.

"The PSI provides major facilities for researchers from Switzerland and all around the world. We develop, build and support these facilities," explained the physicist and research manager. "As our scientists were involved every step of the way and are continually working to refine the methodology, the SLS ranks among the top facilities of its kind in the world." There is so much demand for experimentation time that the plant capacity could be used two to four times over, even though it is in operation around the clock. "Even if you come in here at 3am on a Sunday, you will still find people using it," revealed Oliver Bunk. The researchers from all around the world are supported by PSI scientists, who know the facility inside-out.

Photo: Kellenberger Kaminski Photographie

At the heart of the SLS there is a particle accelerator in which electrons are brought almost to the speed of light. Thick concrete plates shield the electron storage ring which has a circumference of almost 300 metres and which necessitates the round shape of the building. The electrons race around in a vacuum tube, closely bundled together, until they are deviated by magnets at one of 16 points and radiate light – "it is a relativistic effect according to Einstein's theory", explained Oliver Bunk. This so-called synchrotron light is further intensified and bundled in a good half of the 16 beamlines until an extremely stable X-ray beam reaches the test sites which is only half as thick as a hair.

Energy-saving computer chips

Researchers use this brilliant light to investigate new materials for computer chips, for example. Internet or social media platforms require data centres which use as much energy as a major city. If the semiconductors in the microchips could be replaced by a new superconducting material, this would save a lot of energy. However, these materials currently have to be cooled to very low temperatures to enable them to actually conduct electricity loss-free without any resistance. However, the flow of energy becomes very sluggish under normal operating conditions.

Photo: Kellenberger Kaminski Photographie

The causes of this impeded flow of energy were explored by staff from the PSI, together with colleagues from ETH Zurich and the RIKEN research institution in Japan. The scientists X-rayed a material sample which consisted of a combination of oxides, i.e. complex compounds of metals and oxygen. Using synchrotron light, they were able to measure the flow of energy in the boundary layer between the oxides and identify how this distorted the structure of the material. The same phenomenon leads to super-conduction at low temperatures.

These findings, which the team published in January 2016 in the magazine "Nature Communications" will help to alter similar materials specifically in such a way that they also conduct energy loss-free at higher temperatures. A PSI scientist who was involved in the study now works at the Empa. "Don't expect to find microchips made from those materials in your computer or smartphone by as early as next year," warned the expert, "we mainly carry out basic research here which will reap dividends in ten or twenty years."

Better medication

Oliver Bunk is working on imaging processes which are just as important for biology and medicine as they are for materials sciences. As the physicist explained, "it is fascinating how nature builds bones or teeth out of very simple building blocks and structures them to meet the highest quality requirements". Together with dentists, they discovered how to stop micro-cracks at the boundary layers of teeth – which is essential for the stability of the material. The study into bone samples will help in the development of better implants or in achieving progress in the treatment of osteoporosis with medication. Biomedical scientists at ETH Zurich are also among the regular users of the facility.

Since the SLS went into operation in 2001, biologists have also used it to explore the structure of proteins. "These complex molecules are small machines in our bodies which are involved in all our vital functions," explained Oliver Bunk. The study into proteins is also the subject of basic research, although this is as well of interest to medicine and to the pharmaceuticals industry because many diseases are based on malfunctions in those protein molecules. The study into the structure helps to foster a better understanding of those diseases and of the development of new drugs. Half of the funding required for one beamline was provided by Novartis and Hoffmann La Roche, while the Max Planck Society from Germany provided the other half. The PSI implemented another together with Swiss and international pharmaceutical companies.

"We are particularly good at structural biology," said Oliver Bunk. One of the beamlines that was operated from the start even holds a record. It has been used by researchers from across Europe to determine most protein structures; they are now saved in an international database.

A 3D microscope makes details visible on a scale of a few nanometres, thanks to the synchrotron light. The sample is not damaged in the process. (Photo: Kellenberger Kaminski Photographie)

The PSI researchers have developed a new 3D microscope which maps samples like a tomograph without causing any damage to them. The synchrotron light supports a resolution in the nanometre range (a millionth of a millimetre). There is a picture in the hall of the fine structure of porous glass. "If it was a human hair," said Mr. Bunk, "the photograph would fill the entire hall." The 3D microscope can be used to examine tissue samples, for example, in order to study cell growth.

Spin-off company supplies detectors

However, the PSI also notched up a significant success with the development of X-ray detectors. The physicist explained that "while brilliant X-ray sources and good experiments have existed for a long time, there has not been a high-velocity camera that could track precisely what was really happening." The PSI researchers benefited here from the experience that they had gathered from building a detector for the CERN particle physics centre in Geneva. The ideas were transferable, even if the further development took years. The spin-off DECTRIS was founded in 2006. The Baden-Dättwil-based company now has a workforce of over 60 and sells its devices right around the world. "These X-ray detectors have revolutionised research," said Oliver Bunk, adding that "as things stand, we can keep pace internationally very well."

However, the next generation of synchrotron light sources is in development. The PSI is planning an upgrade under the name SLS 2.0 in order to remain at the world's cutting edge in future. This project is also among the strategic projects under way in the ETH Domain. "This does not mean that we are stopping everything here," said Mr. Bunk reassuringly. The intention is to replace the light source, i.e. the accelerator. "The beamlines, which account for a considerable portion of the work and of the funding, will remain," explained the physicist.